The airlines disclosed Thursday that the Federal Aviation Administration had approved transfer of the rights, which are also called slots, earlier this week.

Slots are limited at the busy airport near Manhattan, making them a coveted item when they go on the market.

Last month, American and US Airways agreed to give up some of their slots at LaGuardia and Washington’s Reagan National Airport to settle an antitrust lawsuit that the Justice Department filed to block their merger.

Southwest will get to keep the rights for five takeoffs and landings per day that it was already leasing from American and gain enough slots for six more daily flights. Virgin America will get enough slots for six flights per day. Terms were not disclosed.

In an order approving the transfers, FAA acting chief counsel Marc Warren said they were in the public interest and wouldn’t reduce safety.

Dallas-based Southwest and its AirTran subsidiary already operate 27 daily round-trip flights to and from LaGuardia, and Southwest also flies to Newark, N.J., and Long Island MacArthur Airport. Executive vice president Bob Jordan said the extra slots would expand access to New York for low-fare customers.

Virgin America doesn’t serve LaGuardia. The California-based airline flies to Los Angeles and San Francisco from Newark, and to those two cities plus Las Vegas from New York’s Kennedy Airport.

Virgin had expressed interest in anything that American and US Airways would be forced to give up, including LaGuardia rights, said spokeswoman Abby Lunardini. She said that the airline would announce more details on where it will fly from LaGuardia in the coming weeks.

No decision has been made on who will get the Reagan National slots. American and US Airways also agreed to give up gates at five other airports — Los Angeles International, Boston Logan, Chicago O’Hare, Miami and Dallas Love Field.

The Justice Department sued in August to block the American-US Airways merger, which will create the world’s biggest airline, saying that the deal would reduce competition and cause prices to rise. When it settled the lawsuit before trial, the department said that the takeoff and landing rights and gates that American and US Airways were giving up should go to low-cost airlines and not to big, so-called legacy carriers such United and Delta.